Wicking flow through microchannels

Abstract

We report numerical simulations of wicking through micropores of two types of geometries, axisymmetric tubes with contractions and expansions of the cross section, and two-dimensional planar channels with a Y-shaped bifurcation. The aim is to gain a detailed understanding of the interfacial dynamics in these geometries, with an emphasis on the motion of the three-phase contact line. We adopt a diffuse-interface formalism and use Cahn-Hilliard diffusion to model the moving contact line. The Stokes and Cahn-Hilliard equations are solved by finite elements with adaptive meshing. The results show that the liquid meniscus undergoes complex deformation during its passage through contraction and expansion. Pinning of the interface at protruding corners limits the angle of expansion into which wicking is allowed. For sufficiently strong contractions, the interface negotiates the concave corners, thanks to its diffusive nature. Capillary competition between branches downstream of a Y-shaped bifurcation may result in arrest of wicking in the wider branch. Spatial variation of wettability in one branch may lead to flow reversal in the other.

Microfluidics of imbibition in random porous media

“…For this situation, the curvature of the interface is always maintained (or even increased) and, therefore, the penetration continues. The same behavior has been reported by Mehrabian et al [26] who studied in detail the hydrodynamics of the curvature of the fluid-fluid interface as it passes narrowing and widening channels and also the effect of corners on the contact line. It is to be noted that in the case of the wide-to-narrow capillary [ Fig.…”

Wetting considerations in capillary rise and imbibition in closed square tubes and open rectangular cross-section channels

“…Kusumaatmaja et al, 2008;Clime et al, 2012), numerical simulation using diffuse interface models (e.g. Mehrabian et al, 2011), smoothed particle hydrodynamics (e.g. Tartakovsky & Meaking, 2005) and molecular-dynamics (e.g.…”

An experimental study on the rate and mechanism of capillary rise in sandstone

“…By extending the model presented by Sadjadi et al (2015), l resume can be calculated by Fig. 9 Capillary rise in Y-shaped piping with different radii, as proposed by Mehrabian et al (2011) and Sadjadi et al (2015). Because capillary pressure in narrower pores is greater than that in wider pores, water advances first into narrower pores …”

“…7f ). A theoretical calculation of capillary rise in Y-shaped piping with different pipe radii (Mehrabian et al 2011) indicates that water selectively advances in the narrower pipe because the capillary pressure in the narrower pipe is greater than that in the wider pipe (Fig. 9).…”